Endurance exercise performance has been shown to be limited by oxygen availability to the working muscles. Work rates of individuals partaking in endurance exercise can be increased when oxygen delivery to the working muscle is increased (hyperoxia). Furthermore, cyclists who trained under hyperoxia improved their ability to perform high intensity exercise significantly more than did cyclists who trained under similar conditions but with normal oxygen availability (normoxia).
Regular vigorous exercise has been recognized as a useful therapy for treating patients who suffer from maladies such as cardio- and peripheral vascular diseases. Unfortunately, the effects of many of these diseases prevent prolonged vigorous exercise by restricting the blood flow and thus the rate of oxygen delivery to the working muscle. By increasing the concentration of oxygen in the inspired air, oxygen delivery to the working muscle can be increased, thereby increasing the exercising capacity of these patients and improving the therapeutic use of exercise.
In addition, increasing exercising work rates via hyperoxia increases the rate of caloric (energy) expenditure by the exercising individual. Increasing oxygen availability during exercise has also been shown to increase the body's reliance on stored body fat as an energy source. The rate of obesity among Americans is estimated at 25% and many others are overweight to the point that their health may be impaired. Obesity and high body fat to lean body mass ratios have been associated with increased risk of cardiovascular disease, stroke, hypertension, adult onset diabetes, arthritis and degenerative joint disease. Maintaining healthy weight and body composition is a function of maintaining caloric balance (a balance between caloric consumption and caloric expenditure). Losing weight requires an individual to maintain a negative caloric balance (consume fewer calories than they expend). Traditional methods of attaining negative caloric balance include calorie restrictive diets, increased caloric expenditure through exercise, and a combination of these strategies.
Total caloric expenditure from exercise is determined primarily by the total work performed. The amount of work performed during exercise can be manipulated by either increasing the duration of the exercise period or by increasing the rate at which work is performed. However, work rate is limited by the metabolic capacity of an individual. A primary limiting factor in the metabolic capacity of an individual is the ability to deliver adequate amounts of oxygen to their working muscle. Oxygen is a key ingredient in the process of transforming energy from food and bodily energy stores, for example, fat and carbohydrates, into energy that can be used to fuel muscular contractions. This process of combining oxygen with food to liberate energy is known as aerobic metabolism. When working muscles are supplied with adequate amounts of oxygen, their energy requirements can be met and exercise can be maintained for extended periods of time. Increasing the supply of oxygen to the working muscle increases the rate of aerobic metabolism and the rate of work that can be maintained by the individual. However, when exercising work rates create energy demands that exceed a person's ability to supply energy through aerobic metabolism, the person will fatigue quickly and must either stop exercising or reduce their work rate. Thus, the rates of work and caloric expenditure during exercise can be affected by the availability of oxygen to the working muscle of the individual.
Another benefit of increasing oxygen availability to the exercising individual centers on the use of stored body fat as a source of energy. The two primary sources of energy used by the human body to fuel muscular contractions are carbohydrates and fats. Liberating stored energy from fats requires more oxygen than liberating an equal amount of energy from carbohydrates. Typically, the more oxygen that is available to the working muscle, the more the muscle will rely on fat to meet its energy needs. Thus, in addition to increasing work rate and caloric expenditure, increasing oxygen availability during exercise will increase the body's reliance on fat as an energy source.
The significant aspects of greater fat usage during exercise are twofold: firstly, the catabolism of stored body fat during exercise reduces body fat mass and lowers the ratio of body fat mass to lean body mass. Secondly, greater use of stored body fat reduces the reliance on bodily stores of carbohydrate to fuel muscular contractions. Maintaining adequate stores of carbohydrate is an important aspect of appetite control. The body relies on its stores of carbohydrates for a variety of tasks including the maintenance of blood sugar levels. As bodily stores of carbohydrate drop, so do the levels of sugar in the blood. Low blood sugar has been identified as a major contributor to the stimulation of appetite. Thus, a greater reliance on fat during exercise allows the body to preserve carbohydrate stores, maintain blood sugar levels and suppress appetite following exercise.
Delivery of oxygen to the working muscle has been shown to be affected by the exercising environment. The earth's atmosphere contains 21% oxygen, an oxygen level that is referred to as “normoxic” or “normoxia”. Hyperoxia refers to a condition in which the oxygen levels are higher than 21 percent. Hyperoxic conditions that feature oxygen concentrations that are substantially higher than 21% result in greater oxygen delivery to and higher oxygen consumption by working muscle. The proposed breathing system of the present invention is considered to provide a method to combat obesity and maintain healthy weights and body compositions in individuals.
Devices designed to provide mixtures of gases with variable concentrations of oxygen are known. U.S. Pat. No. 5,915,834 discloses a system using a controller to dial in desired amounts of oxygen and air from gas supply sources through an inlet into a mixing plenum to provide an oxygen mixture. U.S. Pat. No. 5,372,129 discloses an oxygen dilution device for use by patients with respiratory problems, where the device includes a hollow diluter body having a dilution chamber and a vent chamber. U.S. Pat. No. 3,830,257 discloses a device for providing a mixture of air and oxygen to a respiratory mask, where the device includes multiple chambers in communication with the mask and responsive to each other to provide a constant ratio of air to oxygen to the mask. U.S. Pat. No. 3,875,957 discloses an oxygen-air diluter device for breathing apparatus used in high altitude and space flights, where the device includes a casing having oxygen and ambient air inlets and a differential pressure diaphragm, and is designed to control air flow to provide normal air dilution, 100 percent oxygen and pressure breathing. None of the aforementioned devices discloses or suggests use of the control valve system of the proposed breathing system of the present invention as a way to conveniently provide hyperoxic air mixtures for breathing.
Devices designed to provide hyperoxic gas to individuals are widely used in hospital, clinical and home settings. However, most devices do not provide breathing gases at rates that are required during exercise. Other devices designed for exercising individuals have a number of deficiencies that are overcome by the breathing system of the present invention. These deficiencies are as follows:
First, using gas mixtures with oxygen concentrations greater than atmospheric air but less than pure oxygen requires the purchase of cylinders containing premixed gases. While this is possible, it is far more expensive than the cost of equal amounts of pure oxygen and air. Secondly, gases from commercial cylinders are void of moisture and breathing a dry gas mixture during vigorous exercise results in the drying of the upper respiratory tract and the production of mucous causing discomfort and coughing. Thirdly, maintaining the proper rate of gas flow from the oxygen cylinder requires frequent adjustments to the pressure regulator. In current model regulators, the design is such that it is very difficult for the user of the device to adjust the flow of gas from the oxygen cylinder while exercising. Thus, a second individual is needed to monitor and adjust the flow rate from the oxygen cylinder. Finally, in current devices, air flow to the subject is dependent on flow rates from the compressed gas cylinder. In the event that the gas cylinder should empty, air flow to the user stops abruptly. While removing the subject from the device can quickly restore air flow, the brief period in which air flow to the user is stopped is unsettling and does not promote optimal use of hyperoxic training.
The proposed breathing system of the present invention overcomes the aforementioned deficiencies by use of a control valve system to provide an air mixture containing 25–90 volume percent oxygen to the user and at rates that are similar to the ventilation rate of the user. Use of the control valve system of the breathing system of the present invention eliminates the need to purchase pre-mixed breathing gases and the need for manual flow adjustments from compressed oxygen gas cylinders. In addition, lack of moisture in the commercially available gas mixture is overcome by the use of atmospheric air in the breathing system of the present invention.